- The patient has either completed Cephalon study 3079 or has chronic pain of at least 3 months duration prior to entering this study associated with any of the following conditions: diabetic peripheral neuropathy, postherpetic neuralgia, traumatic injury, complex regional pain syndrome, back pain, neck pain, osteoarthritis, or rheumatoid arthritis. Patients with other painful conditions may qualify for the study with permission from the Cephalon medical monitor or designee.